1. Field of the Invention
The present invention relates to a primer composition which is to be applied to a polyolefin material.
2. Background Art
Polyolefin materials exhibit superior properties such as moldability and chemical resistance, and because it is relatively inexpensive, it is widely used in plastic parts in industrial fields in recent years. For example, in an automobile, polyolefin is used for exterior parts such as bumpers or side panels, and it is also used for interior parts such as instrument panels. In these cases, it is usually applied to improve design value and weatherability of the automobile. However, adhesion to polyolefin materials is insufficient, and coatings do not adhere to polyolefin materials, and easily peels off. Therefore, a primer is applied on the polyolefin material to improve adherence before painting. In particular, the primer process is necessary for exterior parts of automobiles such as polyolefin bumpers.
As a primer for polyolefin materials for exterior parts for an automobile which exhibits superior resistance to high-pressure washing and gasohol resistance, a primer composition consisting of chlorinated polypropylene having a specific structure and acrylic denatured chlorinated polypropylene is disclosed in Japanese Unexamined Patent Application Publication No. 31779/96. However, because the primer composition mentioned above requires the molecular weight of acid anhydride denatured chlorinated polypropylene to be in a range of from 30000 to 36000, a process for controlling the molecular weight distribution is required in the producing process of acid anhydride denatured chlorinated polypropylene. Therefore, the price of the primer is increased because the production cost of the primer is higher than that of a usual polyolefin. Therefore, an invention of a primer for a polyolefin material for exterior parts for an automobile which has characteristics of resistance to high-pressure washing and gasohol resistance without adding acid anhydride denatured chlorinated polypropylene which is controlled in a specific range of molecular weight, is required.